In October I brought this new toy home from an auction, and I need to make some mandrels to balance transmission drums. Does the size of the shafts matter? If so, what diameter should they be?
The size of the shafts do not matter, but whatever size they are, they should be the same at each end.
By the way, balancers like this have been shown many times on the forum. I have seen them many times in machine shop grinding departments. They are mainly used to balance grinding wheels, but can be used to balance just about anything.
I would go with 3/4" W-1 drill rod as a minimum. Larger is better. Small rods will flex under the weight of the drums and make it difficult to balance with accuracy. It doesn't take much to throw it off.
I say W-1 because it comes in a mill state at ~RC-40 or better hardness. No further hardening is required. And be sure to balance the mandrels.
I guess a piece of drive shaft or axle shaft would be a good place to start.
Either of those would be a Thrifty source, Mister.
Steve, I think a drive shaft is too large to use on the brake drum unless you turn it down. I am thinking that ¾" rod will be stiff enough and allow you to make collars to handle all 3 drums. I think the d.s. is 1" dia.
The shaft that I use is 1.00" O.D. and the length of the balancer. It is ground stock.....very smooth that is important. I machined the mandrels from aluminum stock which keeps them light. They are fully machined to insure they do not add to any out of balance.
The balancer that I have looks just like yours. Be very careful when placing items to be balance. The bearing points can be damaged easily if you drop something heavy on the rotating wheels.
If you do not have access to a metal lath and the talent to machine the mandrels.....find some one that will help. There are no off-the-shelf mandrels that I know of that are available.
It takes several mandrels to balance a model T transmission including one for the flywheel. It does not take much time to make the mandrels as they are not complicated. I keep a lot of aluminum stock near my lathe in different sizes for tasks like this. If you lived closer we would spend a day making them up. Not rocket science.
Two transmission shafts pointing each direction would make flywheel mandrels unnecessary, I think? Then maybe the brake drum and driven plate can be balanced as a set, even though the diameters differs slightly? Then there are two more drums, maybe one set of conical mandrels can be used for both?
When my mandrel was made I did not have a lathe. My machinist is very good he made one mandrel that fits all the drums by stepping it up in size end to end fitting each drum. Its machined from a solid billet. My blades used to balance are hand saw blades back turned up for a straight flat edge to roll on. There is no advantage I can see to a strong one peace mandrel with about 3/4" ends other then being able to balance all the drums together after balancing separately. The completely machined mandrel needed a few grams drilled off to balance Sounds like Les has the most practical method. Looks like the far left roller in the picture has been balanced.
The balance wheels are independent so diameter tolerance is less important than the straightness of your mandrel shaft (axial runout). Be sure to check that. It needs to be straight.
Balancing the three drums together is a wasted effort and ineffective since the drums rotate independently and are never in the same orbital reference to each other. Simply balance each drum.
When balancing the brake drum, include the driving plate. Depending on how exact you want it, it doesn't hurt to include the push ring. But it's important to index these parts so they go back together the same way.
The same holds true when balancing the flywheel. You could include the disk drum with the key and bolt on the transmission shaft. Keep the balance wheels as close as possible and let the disk drum assembly over hang the wheels. Index, index, index! I use the trans shaft and the third main section off an old crankshaft when balancing a flywheel. And again, straightness is more important than diameter of the two ends--Check runout.
(Message edited by ccwken on January 05, 2016)
Lots of good ideas here. I will borrow a lathe at the juco and get busy. Thanx to all.
One point if you are using the blade balance method is have a good level. My angle iron frame holding the hand saw blades up right has 3/8" bolt leveling feet fastened to a solid bench very carefully leveled with a good level then back checked with a machinist level.
I have never played with the roller type balancer in the picture but the rollers would be checked for balance, nicks, and run out from what ever axel they run on.
Its incredible how much a few grams make out of balance on how shafts rotate.
Henry could not have built and sold the number of Ts he did if he had not excepted a range of balance. We are just narrowing the range more important now with more HP and higher rpms BUT its time consuming.
I do not recommend using two transmission shafts as a method for balancing the flywheel. The lack of being true on all surfaces causing run out and can provide false readings.
Using a 1.00" O.D. ground shaft and machined mandrels helps eliminate that problem. I have also balanced one drum and then balanced the next drum assembled on the first followed by the third drum assembled on the second. Using that method, each drum that is balanced becomes the mandrel for the next drum. This method will save making several mandrels but takes more time and the overall success is dependent on how accurate each drum is balanced in succession.
The best method is balancing each drum separately using individual mandrels.
Just my humble experience.
All, thanks for the information above. Steve and I are both preparing to do this same job and I assume there are lurkers out there planning on the same thing. In the past balancing is a step I skipped over, but want to get it right this time.
It would be great to see a drawing of the design of the mandrel design Les uses. Rather than use knife edges as described above I am attempting to build up a spin balancer to do a dynamic ("two plane") balance. Hopefully my rig will allow static balance to be arrived at first , then dynamic.
I would like to thank those with more experience for contributing to this thread.
Here is my progress on the dynamic balancer so far:
I would guess that your end supports are way too far apart. Any imbalance in the drums will cause that shaft to whip and screw up your results.
Jerry, the supports are adjustable from 4 feet down to about 1 inch. The drums are just sitting on a jack handle in this photo. I still need to add a power jack shaft and motor, ground mandrel, strobe mechanism, and safety straps. I don't know if I will need a vibration dampener like Tom Carnegie used on his machine.
As for imbalance causing the drums to whip around, that is actually the purpose of this machine. If it functions as the pre-electronic balancers did it should allow me to find the imbalance and adjust it out of the drums so that the whipping decreases until it is extinguished. Also, I will balance the drums individually in practice.
If it all works, I should be able to balance a Champaign glass full of coolant on Rusty's radiator cap while the engine is idling!
(Message edited by thorlick on January 05, 2016)
The friction of each bearing using the style shown in your fixture is questionable. The bearings used in the overlapping wheel style balancer that Steve and I have is very sensitive and provide all most no friction. A very different style bearing.
The more bearing friction the less accurate your balancing will be. Using Knife edges may be a much better method.
The mandrels I made are simple shouldered bushings made to fit the shaft (Support) and item to be balanced. The shoulder is especially important when balancing a heavy flywheel.
To this day every one in the know says two plane balancing is necessary. On some parts I am sure they are right BUT I once stuck Dunn weights on using single plane knife edge set up. Then the crank was taken to a professional spin balance shop in Vancouver Washington. I received a call saying they did not know how I did it as the balance was very close and now was dead on with there set up.
I balanced a drive shaft with knives with the knives supporting the bushing surface of a drive shaft the knives had to be 48" apart as I recall
You are correct. I am finding that these surplus bearings will not balance statically. I will probably have to set up knife edges for initial balancing. I think that they should be adequate for the dynamic phase of balancing, however.
Re: mandrels. I was thinking of turning conical collars and sliding them into the bearing of the item to be turned. I suppose the same thing done with a shoulder should be good, if it fits the bearing precisely.
The bed I used for the machine is 4' long so I set it up so I could do drive shafts and axles if I want. I'm not sure that is necessary though.
It should also handle my motorcycle wheels!
My thinking on the whipping is that if the mandrel itself is deflected, (whips), then it too adds to the imbalance and makes it appear that more weight must be removed than is really the case. I readily admit that I have not done any dynamic balancing so my basic understanding may be flawed.
As for static balancing & bearings, I too had trouble with bearings that gave too much resistance to rotation. I removed the seals and washed all the grease out of the bearings. That made a huge difference and I got a really good result in balancing my Model N flywheel. Oddly, it was balanced when it was made but was way out when I checked it. Maybe Ford balanced it on the crankshaft. Whatever the case, it's a very smooth running engine.
It is my belief that a good static balance is adequate for a model T engine or transmission unless you plan on spinning the engine more than 2500 RPM.
Safety is a major concern when considering dynamic balancing. The balance fixture and methods utilized to secure the item to be balanced
must be carefully considered. Heavy items like a flywheel that could come loose may cause a very bad hair day. I suggest you stick to static balancing and leave dynamic balancing to the experts who specialize in it.
Yeah, I'm not sure I'd want to spin a cast iron flywheel to much above that. They tend to start making shrapnel. Even special lathe chucks are needed when you start spinning an 8" above 2500rpm. And they have better iron. (That is, if you're concerned about a safety margin.)
Correct me if I am wrong-----I was told by the spin balance folks there spin test speed was like 750 rpm on the Dunn weight crank I took to them. A spun balanced tire is spun at a relatively low speed comparing to what rpm it works up to. They do have a large shield over the tire while spinning. I would hate to think of a fly wheel loaded with magnets turning at 1000rpm coming out of a fixture in my shop!!
The problem with your set-up is that you are setting the shaft right on the bearings. There is no mechanical advantage as there is in Steve's unit. The mechanical advantage overcomes the friction in the bearing, so if you were to add some disks to the outside of your bearings, you would have a much more sensitive balancing unit.
Very true Paul. Les and I were talking about Engine RPM. I don't know how the Montana racers get away with it. But Ford tested a few engines up around 3000 RPM to show the benefit of a well balanced engine.
My wheel balancer has a hand crank on it. It takes about 2-3 turns before it beeps signifying it's fast enough to balance. Probably not even 200rpm.
I have been working on my balancer as time permits. Today I ran a "proof of concept" test shown here (note test at aprox. 100 rpm):